Change delete older snapshot versions to delete all unknown versions

This task should be executed when the new code is fully deployed to
all machines, and the other snapshot versions are no longer required.

Author: erikrozendaal

lib/sequent/rake/migration_tasks.rb

@@ -391,8 +391,8 @@ def register_tasks!
             desc <<~EOS
               Delete all aggregate snapshots with a lower snapshot version than currently supported.
             EOS
-            task delete_older_versions: :connect do
-              Sequent.configuration.event_store.delete_lower_snapshot_versions
+            task delete_unknown_snapshot_versions: :connect do
+              Sequent.configuration.event_store.delete_unknown_snapshot_versions
               Sequent.logger.info 'Deleted all lower snapshot versions from the event store'
             end
           end